JP6174584B2 - Viewing angle mill - Google Patents

Description

  The present invention relates to charged particle beam milling and, more particularly, to a method for forming a planar cross-sectional view for a scanning electron microscope.

  Charged particle beam systems are used in a variety of applications, including the manufacture, repair, and inspection of devices manufactured by microfabrication techniques, such as integrated circuits, magnetic recording heads, and photolithography masks. Dual beam systems such as the DualBeam instrument sold by the assignee of the present invention, FEI Company, generally have a scanning electron microscope (SEM) capable of providing high resolution images with minimal damage to the target; And an ion beam system such as a focused or shaped beam system (FIB) that can be used for the purpose of modifying the substrate and for forming an image. Such a dual beam system is described, for example, in Hill et al. US Pat. No. 7,161,159, which is hereby incorporated by reference in its entirety. In some dual beam systems, the FIB is tilted from the vertical by an angle, such as 52 degrees, and the electron beam column is oriented vertically. In other systems, the electron beam column is tilted and the FIB is oriented vertically or is also tilted. The stage on which the sample is mounted can generally be tilted, and in some systems the stage can be tilted up to about 60 degrees.

  A common use of dual beam systems is to analyze defects and other defects during microfabrication for troubleshooting, tuning and improvement of the microfabrication process. Defect analysis is useful in all aspects of semiconductor manufacturing, including design verification diagnostics, manufacturing diagnostics, and other aspects of microcircuit research and development. As device geometries continue to shrink and new materials are introduced, the structural complexity of current semiconductors increases exponentially. Many of the structures created by these new materials are re-entrant and penetrate into previous layers. Thus, the structural causes of defects and device failures are often hidden well below the surface.

  Therefore, in defect analysis, it is often necessary to form a cross section and view the defect in three dimensions. The use of copper conductor devices on semiconductor wafers is increasing, and better systems that can perform three-dimensional defect analysis are more important than ever. This is due to the increased number of buried and / or smaller defects and, in many cases, chemical analysis is required. In addition, structural diagnostic solutions that characterize defects and analyze defects need to provide more reliable results in less time, which can be complicated by designers and manufacturers. It is possible to analyze structural defects with certainty, understand the composition of materials and the causes of defects, and increase the yield.

  For example, a dual beam system can be used to detect cavities (voids) in copper interconnect trenches produced by a damascene process. In a typical damascene process, an unfilled trench pattern is formed in the underlying silicon oxide insulating layer to deposit copper conductors. A thick coating of copper that spills significantly from the trench is deposited on the surface of the insulating layer, and then the copper is removed to the level of the top surface of the insulating layer using chemical mechanical planarization. The copper adhering in the trench of the insulating layer is not removed and becomes a patterned conductor. The internal cavity of the copper in the trench can cause open circuit defects. To assess the quality of the fill in the trench, a dual beam system can be used to expose the trench cross section and image the cross section.

  FIG. 1 illustrates a method known in the prior art that exposes a cross-section using a dual beam SEM / FIB system. In order to analyze the features in the sample 102, a section or plane 108 perpendicular to the top surface of the surface 112 of the sample material that has the hidden features to be viewed is typically exposed by a focused ion beam (FIB). Let Since the angle of the SEM beam axis 106 is generally acute with respect to the FIB beam axis 104, a portion of the sample in front of this surface is removed and the SEM beam reaches this surface to image this surface. It is preferable to be able to do so. One problem with this prior art method is that it typically exposes multiple cross sections along the length of the trench in order to form a set of samples of sufficient size to properly evaluate the properties of the trench. It must be.

  For features that are relatively deep with respect to the opening that the FIB opens, this prior art method has the disadvantage of a low signal-to-noise ratio. This situation is similar to the situation where you are trying to create an image of the side of a hole by flashing into a deep hole. For example, a typical copper interconnect trench has a width of 5-8 nanometers (nm) and a depth of 12 nanometers. Many of the electrons from the SEM remain in the trench and do not backscatter to the detector.

  A common application of dual beam systems is in the field of biological science. For example, electron microscopy allows the observation of disease molecular mechanisms, the observation of flexible protein structure tissues, and the behavior of individual viruses and proteins in the natural biological context. One technique that is used in conjunction with electron microscopy, for example to analyze biomaterials, is called “Slice-and-View”. This technique is typically performed using a dual beam SEM / FIB system.

  In this slice-and-view technique, the sample is cut and sliced with high precision by FIB to expose the 3D internal structure or features of the sample. After obtaining an image of the surface by SEM, another substrate layer of the surface can be removed using FIB to expose a new deeper surface and thus a deeper cross section of the feature. Only the part of the feature on the surface that is on the surface is visible to the SEM, so cutting and imaging, i.e., slicing and viewing in turn, reconstructs the sliced sample into a 3D representation of the feature. The data necessary for this is obtained. This 3D representation can then be used to analyze the sample features.

US Pat. No. 7,161,159 US Pat. No. 5,851,413 US Pat. No. 5,435,850

  When processing large sections of a sample, processing of the sample by the slice and view procedure may take a long time. The same can be said when the size of the target feature is relatively small compared to the sample. This is because, in general, the position of the feature portion is not accurately known so that the FIB and SEM beams can be guided to the region of the sample including the target feature portion. Thus, a large section of the sample that appears to contain the feature is processed to locate the feature. Since the typical maximum field of view of an SEM is about 150 microns, slicing, milling and imaging an area of this size can lead to a significant amount of time and use a high resolution setting for the SEM This is especially true when doing so. Alternatively, many smaller parts of the area can be imaged, but doing so results in a huge amount of image data and generally stitches the resulting images together to form a larger composite image It becomes necessary to do. Such a process can currently take hours to days.

  Prior art methods require processing a relatively large section each time the slice-and-view procedure is repeated. This is because the shape or direction of the feature in the sample is not accurately predicted. This problem is particularly exacerbated in the case of certain features having a long and winding shape in the sample, such as in the case of blood vessels or nerves.

  One embodiment of the present invention is directed to a method of forming a planar cross-sectional view for an electron microscope. The method includes directing an ion beam from an ion source toward a first surface of the sample to mill at least a portion of the sample. The method further includes milling the first surface using an ion beam to expose the second surface, wherein the second surface is distal to the second surface as viewed from the ion source. The end is milled to a deeper depth relative to the reference depth than the proximal end of the first surface viewed from the ion source. The method further includes directing an electron beam from the electron source to the second surface. The method further includes forming an image of the second surface by detecting an interaction between the electron beam and the second surface.

  Another embodiment of the invention is directed to a method of forming a cross-sectional view for an electron microscope. The method directs an ion beam from an ion source toward a first surface of the sample to mill at least a portion of the sample, using the ion beam to at least target the first surface. Milling the local area of the feature to substantially flatten at least the local area of the feature of interest on the first surface; after milling the first surface, milling the sample to By exposing a second surface including a cross-section of the feature to be directed, directing an electron beam from an electron source to the second surface, and detecting an interaction between the electron beam and the second surface. Forming an image of the two surfaces.

  Another embodiment of the present invention is a system for forming a cross-sectional plan view for an electron microscope, comprising a focused ion beam column, an electron microscope, a sample stage for holding a sample, and a computer controller. Target the system. The computer controller includes a non-transitory computer readable medium encoded with computer instructions that, when executed by the computer controller, causes the system to mill at least a portion of the sample. In order to do this, an ion beam is directed from the ion source toward the first surface of the sample, and the second surface is exposed by milling the first surface using the ion beam, the second surface The distal end of the second surface viewed from the ion source is milled to a depth deeper than the reference depth than the proximal end of the first surface viewed from the ion source, Further, the second surface is guided by directing an electron beam from an electron source to the second surface and detecting an interaction between the electron beam and the second surface. Forming an image of the surface.

  Another embodiment of the present invention is a system for forming a cross-sectional view for an electron microscope comprising a focused ion beam column, an electron microscope, a sample stage for holding a sample, and a computer controller Is targeted. The computer controller includes a non-transitory computer readable medium encoded with computer instructions that, when executed by the computer controller, causes the system to mill at least a portion of the sample. In order to do this, an ion beam is directed from the ion source towards the first surface of the sample, and the ion beam is used to mill at least a local area of the feature of interest on the first surface. After at least a local area of at least the feature of interest on one surface is substantially flattened and the first surface is milled, the sample is milled to expose a second surface including a cross section of the feature of interest. And directing the electron beam from the electron source to the second surface, and the interaction between the electron beam and the second surface. The image of the second surface formed by detecting.

  For a more complete understanding of the present invention and its advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings.

FIG. 2 illustrates a method known in the prior art for exposing a cross section using a dual beam SEM / FIB system. FIG. 3 shows sample orientation in a dual beam system according to one or more embodiments of the present invention forming a cross-sectional plan view for a scanning electron microscope. FIG. 6 shows a target area 300 of a sample 222 that includes a plurality of feature portions 302-308, for which an SEM image of the feature portion is formed at various lengths along the feature portion in the target area 300; It is hoped to do. It is a figure which shows the cross section of the sample 222 cut | disconnected along the cutting line A-A 'shown by FIG. FIG. 4 shows an ion beam milling the top surface of a sample 222 at a certain glancing angle in accordance with one or more embodiments of the present invention. FIG. 6 is a perspective view of a sample target area after glancing angle milling according to one or more embodiments of the present invention. It is a perspective view of the characteristic part 302 after milling. FIG. 2 illustrates an exemplary dual beam FIB / SEM system that can be used to implement one or more embodiments of the present invention. 6 is a flow diagram illustrating steps in accordance with one or more embodiments of the present invention for performing sample analysis. SEM micrograph showing top planarization of sample and cross section of through silicon via Is true. It is a SEM micrograph which shows sectional drawing of the sample of FIG.

  Although the preferred embodiment of the present invention is directed to a novel defect analysis method suitable for use in semiconductor manufacturing, the present invention can also be used to analyze other types of samples described below. To analyze a semiconductor chip, such as a chip that includes a metal milled trench, sample analysis according to a preferred embodiment of the present invention uses a series of FIBs oriented at right angles as in the prior art. Rather than exposing the cross-section, a viewing angle mill is utilized that directs the FIB to a very small angle with respect to the sample surface, preferably no more than 10 ° to the sample surface.

  Because the ion beam is directed at a small angle relative to the sample surface as shown in FIG. 2, discussed later, the amount of sample material removed by milling is greater on the opposite side of the ion source. That is, the exposed surface is milled deeper at the end of the sample farther from the ion source than at the end closer to the ion source. Thereby, the exposed surface is inclined downward as compared with the original sample surface. In terms of sample features such as trench rows filled with metal, the upper portion of the trench is exposed in the trench closer to the ion source, and the deeper portion is exposed in the trench far from the ion source. After exposing the inclined sample surface, the exposed surface can be imaged from above, for example using an electron beam. With respect to the structural information provided, this exposed bevel image is essentially a combination of a plan view and a plurality of cross-sectional views.

  FIG. 2 illustrates an ion beam milling the top surface of the sample 222 at a viewing angle in accordance with one or more embodiments of the present invention. In the embodiment of FIG. 2, on a pre-tilted standard sample stage (stub) 302 mounted on a tilted sample stage 224 in an ion beam system such as a dual beam SEM / FIB. A sample 222 is attached. A suitable dual beam system is commercially available from, for example, the assignee of the present application, FEI Company (Hillsboro, Oreg.). An example of suitable hardware is shown below, but the invention is not limited to being implemented with any particular type of hardware. In the embodiment of FIG. 2, the electron beam and ion beam are directed so that the electron beam 250 is perpendicular to the untilted sample stage and the angle of the ion beam 218 is about 52 °. In another embodiment, the pre-tilted sample stage 302 is not used and the sample tilt is adjusted by the sample stage tilt and / or column tilt.

  As shown in FIG. 2, the stage is tilted so that the ion beam is incident on the sample surface with a very small viewing angle. The viewing angle is preferably 10 ° or less, more preferably 5 ° or less, and even more preferably 1 ° or less. As used herein, a viewing angle mill refers to milling a sample with an angle between the ion beam and the top surface of the sample of 10 ° or less. In the embodiment shown in FIG. 2, a suitable viewing angle is obtained through the use of a 45 ° sample stage and a stage tilt of 8 ° to 10 °. In this way, the ion beam 218 is guided to the upper surface of the sample 222 with a very small viewing angle of 1 to 3 degrees.

  The actual angle used will depend on the system used and the depth of measurement to be performed. For example, a typical copper interconnect trench is 12 nanometers (nm) deep. The tilt of the sample stage 224 is adjusted so that the angle between the ion beam 218 and the sample 222 is such that the distal end of the target region 300 is cut to a depth of 12 nm. In the embodiment of FIG. 2, the ion beam is directed to a portion that can only be said to be the top surface of the sample, but in some preferred embodiments, the beam is directed deeper into the sample and embedded deeper. Those skilled in the art will appreciate that the features described can be exposed in substantially the same manner.

  FIG. 3 illustrates a target area 300 of a sample 222 that includes a plurality of feature portions 302-308, for which feature SEMs at various lengths along the feature portion in the target area 300. It is desired to form an image. For example, the sample 222 may be a wafer that includes a copper interconnect trench formed by a damascene process. Target area 300 is a portion of sample 222 that includes trenches 302-308, and it is desired to detect copper cavities that may have formed in trenches 302-308 during the damascene process. Part. Although much of the description in this specification is directed to a preferred embodiment in which the sample to be analyzed is a semiconductor chip, the embodiment of the present invention is not limited to biological samples, geological samples, etc. This type of sample can also be targeted.

  FIG. 4 shows a cross section of the sample 222 taken along the cutting line A-A ′ shown in FIG. 3. The feature portions 302-308 extend from the top surface of the sample 222 into the interior of the sample 222 by a given depth (d). For example, a typical copper interconnect trench has a width (w) of 5-8 nanometers (nm) and a depth (d) of 12 nm. In order to investigate defects using prior art methods, a series of time-consuming cross-section cuts along the length of the target area 300 must be performed. Each cross-section is then imaged separately by SEM. As shown in FIG. 5, one or more embodiments of the present invention allow for feature defect detection with improved cycle time and improved signal-to-noise ratio.

FIG. 5 illustrates an ion beam milling the top surface of the sample 222 at a viewing angle in accordance with one or more embodiments of the present invention. According to a preferred embodiment of the present invention, this viewing angle is not a top-down milling angle but a milling angle guided to the edge. That is, instead of directing at a substantially normal angle to the top surface of the sample 222 to expose a vertical surface by a series of vertical cuts, before milling, from the edge of the sample, between the ion beam and the top surface. The ion beam 218 is directed to the sample 222 with a very sharp “sight” angle. This angle is such that, over the entire length of the target area 300, the ion beam 218 mills the top surface of the sample 222 to a predetermined depth (d ₀ ) at the distal end of the target area 300 as viewed from the ion source 214. Selected to mill. After milling, a surface with the sample is exposed in the target area 300 where the distal end 502 of the target area is the depth at which the proximal end 504 of the top surface of the sample 222 in the target area is milled. Instead, it is milled to a deeper depth with respect to the bottom surface of the sample 222.

  The effect of milling at the viewing angle is that the feature 302-308 (only feature 302 is shown) is at least the length of the feature 302 in the target area 300 with a single cut by the ion beam 218. It is to be exposed at various depths along the length. The features 302-308 are then imaged by SEM at various locations along the length of the target area 300 to characterize the characteristics of the features at those locations. Each location corresponds to a different depth, which is based on the angle at which the sample 222 was milled and the distance from the proximal edge of the cut to that location. This is illustrated in FIGS. 6 and 7.

FIG. 6 shows a perspective view of a target area of a sample after glancing angle milling according to one or more embodiments of the present invention. The distal end 502 of the sample 222 is milled deeper than the proximal end 504, and the surface of the sample slopes linearly between these two ends. FIG. 7 shows a perspective view of the feature 302 after milling. The feature 302 is milled to a predetermined depth d ₀ at the distal end 502 of the feature. The proximal end 504 of the feature 302 is little or not milled. Using SEM, imaging along the length of the feature 302 is performed. Because of this glancing angle mill, the surface of the feature 302 is gradually tilted from a depth of 0 nm to d ₀ nm, so that the SEM forms an image at a corresponding position along the length of the feature 302. The characteristics of the feature part can be evaluated at various depths. There is no need to mill individual cross-section cuts at each location, which improves cycle time for defect analysis.

  Furthermore, embodiments of the present invention can also provide improved sample surface imaging compared to general cross-section cutting. In general, when using prior art methods that sequentially expose cross sections in a sample, to expose the sample surface and to provide sufficient space to image the exposed surface, for example by an electron beam A wedge-shaped hole is made in the sample by milling. When this cross section is imaged, some secondary electrons that would otherwise have been used to aid in imaging are lost. This is because secondary electrons collide with the side surface of the wedge-shaped hole. As a result, the signal strength is lost and the signal-to-noise ratio is deteriorated. However, according to one or more embodiments of the present invention, the sample is not pierced by milling to expose the cross section. Instead, the viewing angle mill produces a tilted surface that is more easily imaged and gives an improved signal-to-noise ratio compared to the prior art.

FIG. 8 shows a typical dual beam FIB / SEM system 800 that is used to implement one or more embodiments of the present invention. The focused ion beam system 800 includes an evacuated enclosure 811 having an upper neck portion 812 within which an ion source 814 and a focusing column 816 are located, the focusing column 816 including an extraction electrode and a static electrode. Includes an electro-optic system. The ion beam 818 exiting the ion source 814 passes through the column 816, passes between the electrostatic deflection means shown schematically at 820, and is placed on the movable sample stage 824 in the lower chamber 826. Proceed toward sample 822, eg, sample 822 containing a semiconductor device. An ion pump 828 can be used to evacuate the neck portion 812. Chamber 826 is evacuated by turbomolecular and mechanical pumping system 830 under the control of vacuum controller 832. This vacuum system provides the chamber 826 with a vacuum between about 1 × 10 ⁻⁷ Torr and 5 × 10 ⁻⁴ Torr. When using an etch assisting gas, an etch retarding gas, or a deposition precursor gas, the chamber background pressure may typically rise to about 1 × 10 ⁻⁵ Torr.

  A high voltage power supply 834 is connected to the ion source 814 and suitable electrodes in the focusing column 816 that form and direct the ion beam 818 downward. A deflection controller and amplifier 836 operating in accordance with the determined pattern provided by the pattern generator 838 is coupled to the deflector plate 820, thereby controlling the beam 818 to draw the corresponding pattern on the top surface of the sample 822. it can. In some systems, a deflector plate is placed in front of the last lens, as is well known in the art.

  The ion source 814 typically provides a metal ion beam of gallium, although other ion sources, such as a multicusp ion source, other plasma ion sources, can be used. In order to modify the sample 822 by ion milling, enhanced etching or material deposition, or to image the sample 822, the ion source 814 is typically directed to a beam having a width less than 1/10 microns at the location of the sample 822. Can be focused. Connected to amplifier 842 is a charged particle multiplier 840 that is used to detect the emission of secondary ions or electrons for imaging. The amplified signal is converted into a digital signal by the signal processing unit 843 and subjected to signal processing. The resulting digital signal displays an image of the workpiece 822 on the monitor 844.

  The FIB system 800 further includes a scanning electron microscope 841 and a power supply and control unit 845. By applying a voltage between the cathode 852 and the anode 854, an electron beam 850 is emitted from the cathode 852. The electron beam 850 is focused on a fine spot by the condenser lens 856 and the objective lens 858. The electron beam 850 scans the surface of the sample two-dimensionally by the deflection coil 860. The operations of the condenser lens 856, the objective lens 858 and the deflection coil 860 are controlled by a power supply and control unit 845.

  The electron beam 850 can be focused on the surface of the workpiece 822 on the sample stage 824 in the lower chamber 826. When electrons in the electron beam collide with the surface of the workpiece 822, secondary electrons are emitted. The secondary electrons are detected by a secondary electron detector 840 or a backscattered electron detector 862 connected to the amplifier 842. The amplified signal is converted into a digital signal by the signal processing unit 843 and subjected to signal processing. The resulting digital signal displays an image of the workpiece 822 on the monitor 844.

  A gas delivery system 846 extends into the lower chamber 826 to introduce and direct gas vapor toward the sample 822. US Pat. No. 5,851,413, entitled “Gas Delivery Systems for Particle Beam Processing” by Casella et al., Assigned to the assignee of the present invention, describes a suitable liquid delivery system 246. Another gas delivery system is described in US Pat. No. 5,435,850, entitled “Gas Injection System” by Rasmussen, also assigned to the assignee of the present invention.

  The door 870 is opened to insert the sample 822 onto the sample stage 824 and to use the internal gas supply reservoir if one is used. The sample stage 824 may be heated or cooled. The door is interlocked so that it does not open when the system is in a vacuum. To energize and focus the ion beam 818, the high voltage power supply applies an appropriate acceleration voltage to the electrodes in the ion beam column 816. Dual beam FIB / SEM systems are commercially available from, for example, FEI Company (Hillsboro, Oreg.), The assignee of the present application.

  FIG. 9 is a flowchart 900 illustrating steps in accordance with one or more embodiments of the present invention for performing sample analysis. This method begins with a terminator 902. In step 904, an ion beam 218 is directed to the first surface of the sample 222 to mill at least a portion of the sample 222. In a preferred embodiment, this first surface is the top surface of the sample 222 and the ion beam 218 is not directed at an angle substantially perpendicular to the top surface, but near a top edge at a viewing angle. Led to. At step 906, ion beam 218 mills the first surface to expose the second surface of sample 222. In this second surface, the distal end of the second surface viewed from the ion source 214 is milled to a deeper depth with respect to the reference depth than the proximal end of the first surface viewed from the ion source 214. The That is, along the length of the exposed second surface, the edge of the second surface farther from the beam source is milled deeper than the edge of the second surface closer to the beam source. This depth difference is caused by the angle of the beam with respect to the first surface. Since this angle is a viewing angle, the difference in depth along the entire second surface need only be the same as the depth of the feature to be analyzed. In step 908, the electron beam 250 is directed from the SEM 241 to the second surface to form an image of the second surface. At step 910, an image of at least a portion of the second surface is formed by detecting an interaction between the electron beam and the second surface. For example, secondary electron detector 240 or backscattered electron detector 262 may be used to form an image from secondary electrons emitted when electron beam 250 is directed to the second surface of sample 222. it can. In step 912, the image formed in step 910 is analyzed to determine whether the feature on the second surface has a defect. For example, if the sample is a semiconductor wafer having copper interconnect trenches, the image formed according to the method of FIG. 9 is analyzed to determine the quality of the trench fill, i.e., the cavities in the trenches are detected during plating. can do. For slice-and-view applications, this image can be used as one of a plurality of slices used to build the three-dimensional structure of the feature.

  Viewing angle milling can be used to planarize a limited area of the sample surface. It is not necessary to mill the entire length of the upper surface of the sample 222. In some embodiments of the invention, only a portion of the length of the top surface of the sample 222 is milled. In order to reduce or prevent curing during subsequent cross-section milling operations, a glancing angle mill is performed to flatten the local area near the feature of interest of the sample having an uneven surface. be able to. Curtaining occurs when material is removed at different milling rates. Curtaining can occur when milling features that include multiple materials that are removed at different rates by the same beam. Curtaining can also occur when milling a surface with an uneven shape. For example, the feature of interest may be a through-silicon via (TSV). TSV cross-sectioning is a common practice in semiconductor research facilities to evaluate the properties of cavities and surface interfaces. Due to the depth of the TSV (generally 50-300 nm), milling the cross section of the TSV with an ion beam can result in significant curtaining. By flattening the local area of the TSV on the sample surface with a glancing angle mill before performing the milling of the TSV cross section, the curtaining during the milling of the cross section can be reduced or prevented.

  FIG. 10 is an SEM photomicrograph showing the cross-section of the top planarization of the sample and the through silicon via. The micrograph 1000 shows a sample having an upper surface 1002, a side surface 1004, an upper surface flattened cut portion 1010, a cross-sectional cut portion 1006, and a through silicon via 1008. The upper surface 1002 of the sample has an uneven shape, so that the top-down cross-section forming cut portion is likely to be carated. The upper surface 1002 is, for example, a protective layer such as a platinum protective layer attached to the surface of the sample before forming the cross section. A viewing angle mill is performed on a portion of the upper surface 1002 located above the TSV 1008. This glancing angle mill flattens the local area above the TSV 1008 on the upper surface 1002 to reduce or remove surface irregularities. After performing a glancing angle mill to flatten the local area above the TSV 1008 on the upper surface 1002, a cross-section forming mill is performed to expose the cross section of the TSV 1008. Since the local area above the TSV 1008 on the top surface 1002 is flattened, the carving at the cross section cut 1006 is reduced or eliminated, providing a more convenient cross section of the TSV 1008 for subsequent analysis.

  FIG. 11 is a SEM micrograph showing a cross-sectional view of the sample of FIG. This cross section is milled after the upper surface is flattened by a viewing angle mill. An upper surface flattening cutting portion 1010 substantially flattens a local area above the TSV 1008 on the sample surface. As a result, curtaining in the subsequently milled cross-section cut 1006 is greatly reduced or eliminated, providing a more convenient TSV 1008 cross-section for subsequent analysis.

  Accordingly, a preferred embodiment of the present invention is a method of forming a planar cross-sectional view for an electron microscope, wherein an ion beam is emitted from an ion source toward a first surface of a sample to mill at least a portion of the sample. And using an ion beam to mill the first surface to expose the second surface, wherein the second surface is distal to the second surface as viewed from the ion source. The end is milled to a depth that is deeper than the proximal end of the first surface as viewed from the ion source, and the method further includes directing the electron beam from the electron source to the second surface. A method is provided that includes guiding and forming an image of the second surface by detecting an interaction between the electron beam and the second surface. The method may further include analyzing the image of the second surface to determine whether the second surface feature includes a defect.

  Embodiments of the present invention include a method in which the angle between the first particle beam and the first surface is 10 degrees or less, and a method in which the angle between the first particle beam and the first surface is 5 degrees or less. A method in which the angle between the first particle beam and the first surface is less than 1 degree, a method in which the ion beam includes a focused ion beam, a tilt of the sample stage on which the sample is mounted, Including a method of changing between a step and an image forming step, and a method in which a 45 degree platform is placed between the sample stage and the sample.

  A preferred embodiment of the present invention is further a method of forming a cross-sectional view for an electron microscope, wherein an ion beam is directed from an ion source toward a first surface of a sample to mill at least a portion of the sample. Using an ion beam to mill at least a local area of the target feature of the first surface to substantially flatten the local area of at least the target feature of the first surface. After milling the first surface, milling the sample to expose the second surface including the cross-section of the feature of interest, directing an electron beam from the electron source to the second surface; and A method is provided that includes forming an image of the second surface by detecting an interaction between the electron beam and the second surface. The method may further include analyzing the image of the second surface to determine whether the second surface feature includes a defect.

  Embodiments of the present invention include a method in which the angle between the first particle beam and the first surface is 10 degrees or less, and a method in which the angle between the first particle beam and the first surface is 5 degrees or less. A method in which the angle between the first particle beam and the first surface is less than 1 degree, a method in which the ion beam includes a focused ion beam, a tilt of the sample stage on which the sample is mounted, Including a method of changing between a step and an image forming step, and a method in which a 45-degree table is placed between the sample stage and the sample.

A preferred embodiment of the present invention is further a system for forming a cross-sectional plan view for an electron microscope, encoded with a focused ion beam column, an electron microscope, a sample stage holding a sample, and computer instructions. A computer controller comprising a non-transitory computer readable medium, wherein when the computer instructions are executed by the computer controller, the computer instructions cause the system to
Directing an ion beam from an ion source toward the first surface of the sample to mill at least a portion of the sample;
Milling the first surface using an ion beam to expose the second surface;
In this second surface, the distal end of the second surface viewed from the ion source is milled to a depth deeper than the reference depth than the proximal end of the first surface viewed from the ion source. And the system further
Directing an electron beam from the electron source to the second surface;
Providing a system for forming an image of the second surface by detecting an interaction between the electron beam and the second surface;

  The computer readable medium may further be encoded with computer instructions for analyzing the image of the second surface to determine whether the feature of the second surface includes a defect.

  Embodiments of the present invention include a system in which the angle between the first particle beam and the first surface is 10 degrees or less, and a system in which the angle between the first particle beam and the first surface is 5 degrees or less. A system in which the angle between the first particle beam and the first surface is less than or equal to 1 degree; a system that changes the tilt of the sample stage on which the sample is mounted between the milling step and the imaging step; And a system in which a 45 degree platform is placed between the sample stage and the sample.

A preferred embodiment of the present invention is further a system for forming a cross-sectional view for an electron microscope, encoded with a focused ion beam column, an electron microscope, a sample stage holding a sample, and computer instructions. A computer controller comprising a non-transitory computer readable medium, wherein when the computer instructions are executed by the computer controller, the computer instructions cause the system to
Directing an ion beam from an ion source toward the first surface of the sample to mill at least a portion of the sample;
Using an ion beam to mill at least the local area of the target feature of the first surface to substantially flatten the local area of at least the target feature of the first surface;
After milling the first surface, the sample is milled to expose the second surface including the cross-section of the feature of interest;
Directing an electron beam from the electron source to the second surface;
Providing a system for forming an image of the second surface by detecting an interaction between the electron beam and the second surface;

  The computer readable medium may further be encoded with computer instructions for analyzing the image of the second surface to determine whether the feature of the second surface includes a defect.

  Embodiments of the present invention include a system in which the angle between the first particle beam and the first surface is 10 degrees or less, and a system in which the angle between the first particle beam and the first surface is 5 degrees or less. A system in which the angle between the first particle beam and the first surface is less than 1 degree, a system in which the ion beam includes a focused ion beam, a tilt of the sample stage on which the sample is mounted, Including a system that varies between the step and the imaging step and a system in which a 45 degree platform is placed between the sample stage and the sample.

  While the above description of the present invention is primarily directed to sample analysis methods, it should be recognized that apparatus for performing such method operations are also within the scope of the present invention. It should further be appreciated that embodiments of the present invention can be implemented by computer hardware or software, or a combination of hardware and software. The method of the present invention can be implemented as a computer program based on the methods and figures described herein using standard programming techniques. The computer program referred to herein includes a computer-readable storage medium configured to include a computer program, and the storage medium configured in such a manner causes the computer to be in a predetermined manner. Make it work. Each program can be implemented in a high level procedural or object oriented programming language to communicate with a computer system. However, if desired, these programs can be implemented in assembler language or machine language. In any case, the language can be a compiled or interpreted language. Further, the program can be executed on a dedicated integrated circuit that is programmed to execute the program.

  Further, the methodology is, but is not limited to, being separate from the charged particle tool or other imaging device, integral with the charged particle tool or other imaging device, or communicating with the charged particle tool or other imaging device. It can be implemented on any type of computing platform, including a personal computer, minicomputer, mainframe, workstation, networked or distributed computing environment, computer platform, and the like. Aspects of the invention may be on a storage medium or storage device, such as a hard disk, optical read and / or write storage medium, RAM, ROM, whether removable or integral with a computing platform. Machine readable code stored above, wherein the programmable computer configures the computer when reading the storage medium or storage device to perform the procedures described herein; It can be implemented as machine-readable code stored for reading by the computer for operation. Further, the machine readable code or a portion of the machine readable code can be transmitted over a wired or wireless network. The invention described herein includes these various types of computer-readable storage media, including instructions or programs that implement the steps described above in conjunction with a microprocessor or other data processing apparatus, and various others. Various types of computer readable storage media. The invention further includes a computer programmed according to the methods and techniques described herein.

  A computer program may be used on the input data to perform the functions described herein, thereby converting the input data to generate output data. This output information is output to one or more output devices such as a display monitor. In a preferred embodiment of the present invention, the transformed data represents a physical real object, which includes generating a specific visual representation of the physical real object on the display screen. .

  Preferred embodiments of the present invention further utilize particle beam devices such as FIB, SEM, etc. to image the sample using the particle beam. Such particles used to image the sample inherently interact with the sample, so that the sample is physically deformed to some extent. Further, throughout this specification, discussions using terms such as “analyze”, “calculate”, “determine”, “measure”, “generate”, “detect”, “form”, etc. Relates to the operation and processing of a computer system or similar electronic device, which manipulates data represented as physical quantities in the computer system and uses that data to the same computer computer. The data is converted into other data similarly expressed as a physical quantity in the system or other information storage device, transmission device or display device.

  The present invention has broad applicability and can provide many of the advantages described and shown in the examples above. Embodiments of the present invention vary greatly depending on the specific application. Not all embodiments provide all these advantages, and not all embodiments achieve all the objectives achievable by the present invention. A particle beam system suitable for practicing the present invention is commercially available, for example, from FEI Company, the assignee of the present application.

  Although much of the above description is directed to semiconductor wafers, the present invention can be used with any suitable substrate or surface. Furthermore, when the terms “automatic”, “automated” or similar terms are used herein, these terms are either automated processes or automated steps or automated processes or automated steps manually. It is understood to include the beginning. In the discussion and claims that follow, the terms “including” and “comprising” are used as open-ended terms, and thus these terms are: It should be construed to mean "including but not limited to". The term “integrated circuit” refers to a set of electronic components patterned on the surface of a microchip and their interconnections (collectively internal electrical circuit elements). The term “semiconductor device” refers generically to an integrated circuit (IC) that is integral with or separated from a semiconductor wafer or for use on a circuit board. It may be packaged. The term “FIB” or “focused ion beam” is used herein to refer to a parallel ion beam, including a beam focused by ion optics and a shaped ion beam.

  Unless otherwise defined herein, the terms are intended to be used in their ordinary general meaning. The accompanying drawings are intended to aid in understanding the invention and are not drawn to scale unless otherwise indicated.

  Having described the invention and the advantages of the invention in detail, various changes, substitutions and modifications can be made to the specification without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that it can. Furthermore, it is not intended that the scope of the application be limited to the specific embodiments of the processes, machines, manufacture, compositions, means, methods, and steps described herein. Those skilled in the art will readily understand from the present disclosure that existing or future developments that perform substantially the same function or achieve substantially the same results as the corresponding embodiments described herein. Any process, machine, manufacture, composition, means, method or step that may be employed may be utilized in accordance with the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

Claims (14)

A method of forming a figure for an electron microscope,
Directing a focused ion beam from an ion source toward the first surface of the sample to mill at least a portion of the sample, and milling the first surface using the focused ion beam; Exposing a second surface, wherein a distal end of the second surface viewed from the ion source is a proximal end of the first surface viewed from the ion source. Than the reference depth, and the method further comprises:
Directing an electron beam from an electron source to the second surface ;
Forming an image of the second surface by detecting an interaction between the electron beam and the second surface, the image including at least a portion of a feature of interest;
Evaluating the characteristics of the feature of interest at a plurality of positions along the image of the second surface; and
Determining a depth of each of the plurality of positions based on a distance of the position from a proximal end of the image viewed from the ion source and an angle between the ion beam and the first surface. A method involving>.   The method of claim 1, further comprising analyzing the image of the second surface to determine whether a feature of the second surface includes a defect.   The method of claim 1 or 2, wherein milling the sample to expose a second surface further comprises directing the ion beam to the first surface at an angle of 10 degrees or less.   4. The method of claim 1, wherein milling the sample to expose a second surface further comprises directing the ion beam to the first surface at an angle of 5 degrees or less. The method described.   5. The method of claim 1, wherein milling the sample to expose a second surface further comprises directing the ion beam to the first surface at an angle of 1 degree or less. The method described.   The method according to any one of claims 1 to 5, wherein a tilt of a sample stage on which the sample is mounted is changed between the milling step and the imaging step.   The method according to any one of claims 1 to 6, wherein a 45-degree table is disposed between the sample stage and the sample. A method of forming a figure for an electron microscope,
Directing a focused ion beam from an ion source toward the first surface of the sample to mill at least a portion of the sample;
Using the focused ion beam, at least a local area of the target feature of the first surface is milled to substantially reduce at least the local area of the target feature of the first surface. Flattening,
After milling the first surface, the ion beam is directed to the first surface at an angle of 10 degrees or less, the sample is milled, and the second surface includes a cross section of the feature of interest. Exposing,
Directing an electron beam from an electron source to the second surface ;
Forming an image of the second surface by detecting an interaction between the electron beam and the second surface ;
Evaluating the characteristics of the feature of interest at a plurality of positions along the image of the second surface; and
Determining a depth of each of the plurality of positions based on a distance of the position from a proximal end of the image viewed from the ion source and an angle between the ion beam and the first surface. A method involving>.   The method of claim 8, further comprising analyzing the image of the second surface to determine whether a feature of the second surface includes a defect.   10. A method according to claim 8 or 9, wherein the ion beam is directed to the first surface at an angle of 5 degrees or less.   11. A method according to any one of claims 8 to 10, wherein the ion beam is directed to the first surface at an angle of 1 degree or less.   12. A method according to any one of claims 8 to 11, wherein the tilt of a sample stage on which the sample is mounted is varied between the milling step and the imaging step.   The method according to any one of claims 8 to 12, wherein a 45 degree platform is arranged between the sample stage and the sample. A system for forming a figure for an electron microscope,
A focused ion beam column;
An electron microscope,
A sample stage for holding the sample;
A computer controller comprising a non-transitory computer readable medium encoded with the computer instructions, and when the computer instructions are executed by the computer controller, the computer instructions cause the system to A system for executing the method according to claim 13.

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